Step 1: Open the Settings app by either clicking on the App Tray in the bottom left corner and then the Settings icon, or by clicking on the time in the bottom right, and then the Settings icon. Then, click on Device on the left side of the window. Then, click Keyboard and Inputs.
Step 2: Scroll down and click on Input Settings.
Step 3: Click Add input methods.
Step 4: Click the checkbox next to English (US) with International keyboard.
Now that you have the international keyboard set up, you will have to change between the US keyboard and the international keyboard each time you want to type accents.
Step 5: Click on the US symbol next to the pen icon in the bottom right of your screen, then select English (US) with International Keys.
The US icon will change to IN to indicate that you have the International keyboard selected.
Step 6: Type using the international keyboard's shortcuts for accent marks. Some of the main ones include:
' + letter --> á
`(found next to the 1 key) + letter --> à
~ + letter --> ã
^ + letter --> â
" + letter -->ä
right alt + ! or ? --> ¡ ¿
Step 7: To return to the normal US keyboard, repeat step 5 and select English (US).
Updated 8/22/24. Screenshots reflect user experience on ChromeOS version 127.